Most sites such as Zillow get their data from other online databases including local MLS systems rather than the actual listing agents. Therefore, agents have little or no control over online listings. Most MLS systems give only a couple days for agents to change the listing to closed.
Zillow estimates or Zestimates are not appraisals and are not very accurate. An accurate appraisal will have to come from a qualified real property appraiser. However, you can use the homes in your area that are for sale and the ones that have recently sold to make your own judgement. Try to look at similar homes. The zillow map will show homes for sale in your area as well as recently sold homes.
I see many agents offering "short sale" as a solution. A short sale will damage your credit and you can still be held liable for the difference between the sale amount and the amount you owed, even after your home is sold. First, have a licensed appraiser do an appraisal to determine the most accurate value of your home. If the value is significantly lower than what you owe, you have two options if maintaining your credit is your goal. You can either rent it or stay put.
Installing a radiant barrier in the attic can reduce your heating and cooling cost. A radiant foil barrier installed under the rafters will reflect a large percentage of the heat that is absorbed by the roof in the summer and contain the heat that escapes the living space into the attic during the winter. It can be installed on the attic floor also. However, it will need to be a perforated foil barrier to allow the rise and evaporation of moisture, especially in humid climates. This may be an effective way of lowering your energy bill. However, there are claims that suggest that placing the barrier under your rafters can reduce the life of your roofing. Radiant barriers are available at Lowes and Home Depot. They look like a giant roll of tin foil.